About types of dams and purpose of dams

2. PRESENTATION
TOPIC:
DAMS
PRESENTED TO:
SIR DAWOOD-UL-HASSAN
PRESENTED BY:
ABDUL MUTAKABER
BSCT01133006

3. Dams
 Definition:
Dam is a solid barrier constructed at a suitable location across a river
valley to store flowing water.
 Storage of water is utilized for following objectives:
• Hydropower
• Irrigation
• Water for domestic consumption
• Drought and flood control
• For navigational facilities
• Other additional utilization is
to develop fisheries

4. TYPES OF DAMS
1. GRAVITY DAMS:
• These dams are heavy and massive wall-like structures of concrete in
which the whole weight acts vertically downwards.
• Bhakra Dam is the highest Concrete Gravity dam in Asia and Second
Highest in the world.
• In a gravity dam, the force that holds the dam in place against the
push from the water is Earth’s gravity pulling down on the weight of
the dam itself.
• In a gravity dam, stability is secured by making it of such a size and
shape that it will resist overturning, sliding and crushing at the toe.

5. TYPES OF DAMS
2. ARCH DAMS:
• An arch dam is a type of dam that is curved and commonly built with
concrete.
• The arch dam is a structure that is designed to curve upstream so that
the force of the water against it, known as hydrostatic pressure.
• An arch dam is most suitable for narrow gorges or canyons with steep
walls of stable rock to support the structure and stresses.

6. TYPES OF DAMS
3. EARTH DAMS:
• An embankment dam is a massive artificial water barrier. They are
mainly built with clay, sand and gravel, hence they are also known as
Earth fill dam or Rock fill dam.
• They are trapezoidal in shape.
• Earth dams are constructed where the foundation or the underlying
material or rocks are weak to support the masonry dam or where the
suitable competent rocks are at greater depth.
• Earthen dams are relatively smaller in height and broad at the base.
 DISADVANTAGE:
• Water can easily pass through it.
• less durable than other type dams.
• The height of this dam is less.

7. SELECTION OF SITES
1. Topographically:
• Place must be suitable.
• Narrow gorge or small valley with enough catchment areas.
2. Technically:
• Should be strong, impermeable, and stable.
• Strong rocks leads to better designs.
• impermeable sites ensures better storage
• Stability with reference seismic shocks and slope failures around the
dam are a great relief to the public as well as the engineering.
3. Constructionally:
• Should be not far off from deposits of materials which would be
useful for construction
• Natural materials of construction Like earth, sand, gravel,
and rock should be easily feasible otherwise cost will increase.

8. SELECTION OF SITES
4. Economically:
• Benefits arising should be realistic and justified in terms
of land irrigated or power generated or floods averted or water
stored.
5. Environmentally:
• The site of the dam should not involve ecological disorder (in the
life of plants, animals and man).
• The fishes in the streams are also affected, so things should also be
considered.
• The dam and the associated reservoir should become an acceptable
element of the ecological set up of the area.

9. FORCES ACTING ON A DAM
1. Weight Of The Dam:
• In gravity dams and embankment dam the weight of the dam is the
major force acting for holding the water back on the upstream side.
• The forces arising due to the weight of the dam are compressive in
nature.
2. Water Pressure:
• The dam is required to resist horizontal forces acting due to weight of
the water impounded on it.
• This water pressure can be calculated by hydrostatic pressure
distribution.
3. Earthquake Forces:
• The disturbance in dams is highly dangerous because they store huge
volumes of water.
• Dams built in the areas known to be seismically active must be
designed to withstand additional forces that are likely to arise in a
future shock.

10. FORCES ACTING ON A DAM
4. Uplift Pressure :
• It is almost impossible to make a dam impervious structure.
• Many minute cracks and pores are left in the dam and the foundation
body.
• Water is likely to find its way into these minute openings through
seepage and gradually fill them up.
• It exerts an upward pressure on the body of the dam.

11. MAIN CAUSES OF DAM FAILURE
 Common causes of dam failure include:
• Sub-standard construction materials/techniques.
• Spillway design error.
• Geological instability caused by changes to water levels during
filling or poor surveying.
• Sliding of a mountain into the reservoir.
• Poor maintenance, especially of outlet pipes.
• Extreme inflow.
• Human, computer or design error.
• Internal erosion, especially in earthen dams.

12. MAIN CAUSES OF DAM FAILURE

13. CONCLUSION
 Generally there are mainly the three types of dam which are
selected on the basis of need of water requirement and our basic
need such as :-
• Hydropower
• Irrigation
• Water for domestic consumption
• Drought and flood control
• For navigational facilities
• Other additional utilization is to develop fisheries
• Due to some of the carelessness while the construction it hampers
the life and strength so it is necessary to study the basic concept of
the dams.
• Utilization of dam water also promotes the production of the
hydroelectricity.